Vibratory grinding



April 1963 H. PODMORE 3,084,876

- VIBRATORY GRINDING Filed Feb. 24, 1959. 2 Sheets-Sheet 1 29 T 2/ 27 T T T T Inventor HENRY L. PODMORE s g m i A tlorneys April 9, 1963 H. PODMORE VIBRATORY GRINDING 2 Sheets-Sheet 2 Filed Feb. 24. 1959 Inventor HENRY L. PODM R 3,084,876 VIBRATORY GING Henry Leveson Podmore, Wildacres, Consall, near Wetiey Rocks, Stoke-on-Trent, Staifordshire, England Filed Feb. 24, 1959, Ser. No. 795,223 9 Claims. (Qt. 241-19) This invention relates to vibratory grinding and is concerned with an improved method of carrying out the grinding of both Wet or dry materials by the vibratory method, and also with improved apparatus for carrying the method into effect.

The invention consists in feeding a charge into the chamber of a mill which contains grinding media, subjecting the chamber to vibratory action, and introducing air under pressure into the lower part of the chamber to iluidise the charge, and thereby facilitating free movement of the grinding media.

The air flow is maintained sufiiciently strong to create classification of the charge within the mill chamber so that the finer particles will rise to the top of the charge, and the upward flow of air is used to carry off these finer particles from the top of the charge by way ofan outlet in the upper part of the chamber.

The material, in a dry state, can therefore be fed continuously into the chamber, either through an inlet chute or by being blown in along with the air, and continuous grinding of dry material can take place in an open circuit, since only the fine particles will be removed, the coarser ones remaining for further grinding action.

The particles removed may however be subjected to a classifying treatment and over-size ones returned to the mill chamber for further grinding action.

In some cases it may not be necessary to provide means for vibrating the chamber; in the case of some friable or granular materials, for instance, the air introduced to fluidise the charge may itself create sufiicient agitation for grinding action.

In the case of wet materials the fiuidisation of the charge by air introduced at the bottom is still advantageous but in this case it is not possible to carry out continuous grinding in an open circuit, since the air flow cannot be used to carry away the fine particles.

Apparatus for carrying out the method comprises a mill chamber containing suitable grinding media, one or more air inlets in the lower part of the chamber, one or more outlets in the upper part of the chamber, and means for creating a vibratory movement of the charge in the chamber.

The invention will be further described with reference to the accompanying drawingswhich show by way of example an apparatus for carrying out the invention aforesaid.

In the drawings:

FIGURE 1 is a diagrammatic side view partly in section.

FIGURE 2 is a plan.

FIGURE 3 is a section on line AA of FIGURE 5.

FIGURE 4 is a section on line BB of FIGURE 5.

FIGURE 5 is a plan of the mill chamber.

The apparatus consists of a mill chamber containing suitable grinding media 11 and mounted on a horizontal platform 12. The platform is carried on the upper ends of a number of springs 13 attached to a lower platform 14 which is subjected to vibratory action by a vibrator unit 15 of any suitable known type. The chamber 10 has an inverted conical bottom portion 16 and a top cover 10 there is a bottom air inlet 16 (or possibly more than one) and an outlet duct or passage, which may be in the form of a rubber or other flexible pipe 20, is connected to the cover for carrying away the fine particles with the air stream. The pipe 20 leads to tes atent the upper end of a classifier 21, from the lower end of which a return pipe 22 takes oversize material back to the mill chamber 10 for further grinding action. The return pipe 22 is controlled by a valve 23 which may be in the form of a motorised rotary valve. The finer material passes from the upper part of the classifier 21 through a duct 26 leading to a separator such as filter bags or, as shown, a pair of cyclones 27, where the fine particles are separated from the air stream and dust and are collected in bags 28. The air stream and dust passes from the cyclones through a further duct 29 to a dust collector 30. The lower parts of the cyclones may be fitted with receiving hoppers 32 to which the bags 28 are attached. The dust may be deposited into a bag 31 by way of a funnel 33 at the bottom of the dust collector.

The material to be ground is delivered into an inlet chute 35 in the upper part of the mill chamber 10-. The inlet chute is fed by means of a vibratory or other type of feeder 36 from a hopper 37. The inlet chute35 has a bottom plate 38 which has holes 39 in it through which the material falls into the mill chamber.

For controlling the velocity of the air flow in the upper part of the mill chamber 10 one or more depending tubes 40 whose upper ends are open to atmosphere are slidably mounted in guides 41 in the top cover 10 of the mill chamber so that they may be made to depend into the chamber to a greater or lesser extent. The actual air flow through the tubes 40 is constant but by lowering the tubes into the chamber a greater current of air sweeps over the charge because of the effective reduction of the area of the path of its fiow to the discharge outlet 20, so forming a dense cloud which moves towards the outlet 20. The lower the tubes, the coarser will be the product discharged through outlet 20. Thus, the arrangement provides a dorm of clasisfication and, to some extent, control of the removed particle size.

It would be possible to control the feed into the mill chamber automatically from the back pressure in the air circuit, by so arranging that when a suihcient quantity of material is in the chamber the back pressure encountered by the air will operate means for shutting off the feed until the pressure falls again. For instance the air inlet 16 may incorporate a pressure responsive valve controlling an electrically driven apparatus for feeding the material into the chamber, either along with the air or through a separate inlet.

It will be understood that when an external vibrator is used to vibrate the mill chamber, the amount of movement will be-very small, perhaps barely perceptible, but of a fairly high frequency. The amount of air introduced with the object of fluidising the charge will need to be adjusted in relation to the cross-sectional area of the chamber, and the amount of charge, so that an even distribution of the charge among the grinding media will be maintained, and so that the finer particles will rise to the top. The inverted conical shape of the bottom part of the chamber assists in this, and ensures that the whole charge will be fluidised, that is to say, will behave as a fluid under the action of the air pressure.

The invention provides an effective method and means for vibratory grinding which will be rapid in its operation and economical in the power needed to operate it.

I claim:

1. A method of grinding comprising placing a charge into a chamber containing grinding media, subjecting the chamber to a vibratory action, and continuously introducing air at the lower portion of the chamber and removing same from the upper portion thereof to fluidize the charge prior to removal thereof from the chamber.

2. A method of grinding and classifying, characterized by feeding a charge into a vibratory chamber containing freely movable grinding media, introducing air under pressure into the lower part of said chamber to fluidize the charge and thereby facilitate free movement of said grinding media, con-ducting said fluidized charge into a classifier, and returning coarser particles from said classiher to said charge chamber.

3. A method of grinding comprising: introducing into a chamber containing a grinding media a charge of material to be ground; subjecting the media and material to agitation thereby to grind said material; continuously introducing a gas into the lower portion of the chamber to fluidize the material during the grinding of said material, and continuously removing said gas together with ground particles from the upper portion of the chamber.

4. A method of grinding comprising: introducinginto a chamber containing a grinding media a charge of material to be ground; subjecting the media and material to agitation thereby to grind said material; continuously introducing a gas into the chamber to fluidize the material during the grinding and to continuosuly remove the ground particles from the upper portion of the chamber, said gas including a stream directed into the upper part of said chamber and against the top surface of said charge.

5. A vibratory grinding mill comprising a resiliently mounted grinding chamber having a top wall .and adapted to contain grinding media for acting upon a charge of material to be ground, vibratory means connected thereto, the lower part of the chamber having inclined walls by which its area in horizontal cross-section increases uniformly with increase in height, means at the base of the chamber Where its horizontal cross-sectional area is smallest for introducing a flow of air which will consequently rise up through the charge and fluidize it, inlet means in the upper part of the chamber for introducing material to be ground, a discharge outlet in the upper zone of the chamber for withdrawing air and ground particles of the material, and duct means separate from said inlet means for admitting a stream of air to the upper part of the chamber to strike the top surface of the charge of material to be ground in the chamber.

6. LA grinding apparatus comprising a grinding mill structure defining a chamber having a top Wall and adapted to contain a plurality of unsecured grinding media, means for vibrating said chamber, inlet means for introducing material to be ground into the top of said chamber, means for introducing air into the bottom of said chamber to fiuidize the material and media, a discharge outlet in the upper part of the chamber :for withdrawing air and ground particles of the material, and duct means separate from said inlet for injecting a stream of air into the upper part of the chamber against the surface of the charge of material to be ground.

7. A grinding apparatus according to claim 6 wherein said duct means for injecting a stream of air comprises at least one tube adjustable to difierent levels in the upper part of said chamber for controlling the velocity of said air and regulating the coarseness of the ground particles withdrawn through said discharge outlet.

aos gsre 8. A vibratory mill comprising a resiliently supported grinding chamber that is cylindrical about a vertical axis and having a top Wall, said chamber being adapted to contain unsecured grinding media for acting on a charge of material to be ground, vibrating means connected to said chamber for vibrating it with its contained grinding media and charge of material to be ground, a chute depending from said top Wall centrally into said chamber for introducing material to be ground into said chamber and restricting the surrounding portion of said chamber to an annular space, said chamber having a discharge outlet in the upper annular portion thereof for discharging the ground particles of material, and means in communication with said chamber for injecting a gaseous medium into said chamber to fluidize the material to be ground as the latter is vibrated and to exhaust the ground particles and gaseous medium through said discharge outlet, said gaseous medium injecting means including .at least one inlet duct in the upper annular portion of said chamber separate from said chute and discharge outlet for injecting a stream of gaseous medium onto the body of the charge of material.

9. A vibratory mill comprising a resiliently supported grinding chamber that is cylindrical about a vertical axis and having a top wall, said chamber being adapted to contain unsecured grinding media for acting on a charge of material to be ground, vibrating means connected to said chamber for vibrating it with its contained grinding media and charge of material to be ground, the lower part of said chamber having upwardly diverging walls concentric about its vertical axis and by which its area in horizontal cross section increases with increase in height, said chamber having an inlet in the upper portion thereof for admitting material to be ground and also having a discharge outlet in the upper portion thereof for discharging the-ground particles of material, and means in communication With said chamber -for injecting a gaseous medium into said chamber to flnidize the material to be ground as the latter is vibrated and to exhaust the ground particles and gaseous medium through said discharge outlet, said gaseous medium injecting means including at least one inlet duct in the upper portion of said chamber separate from both said material inlet and discharge outlet for injecting a stream of gaseous medium onto the body of the charge of material.

References Cited in the file of this patent UNITED STATES PATENTS 936,645 Tuckenbach Oct. 12, 1909 1,762,381 Birch June 10, 1930 2,192,549 Hadsel Mar. 5, 1940 2,607,537 Shaw Aug. 19, 1952 2,778,577 Linke Ian. 22, 1957 2,819,849 Becker Jan. 14, 1958 FOREIGN PATENTS 494,892 Great Britain Nov. 2, 1938 

5. A VIBRATORY GRINDING MILL COMPRISING A RESILIENTLY MOUNTED GRINDING CHAMBER HAVING A TOP WALL AND ADAPTED TO CONTAIN GRINDING MEDIA FOR ACTING UPON A CHARGE OF MATERIAL TO BE GROUND, VIBRATORY MEANS CONNECTED THERETO, THE LOWER PART OF THE CHAMBER HAVING INCLINED WALLS BY WHICH ITS AREA IN HORIZONTAL CROSS-SECTION INCREASES UNIFORMLY WITH INCREASE IN HEIGHT, MEANS AT THE BASE OF THE CHAMBER WHERE ITS HORIZONTAL CROSS-SECTIONAL AREA IS SMALLEST FOR INTRODUCING A FLOW OF AIR WHICH WILL CONSEQUENTLY RISE UP THROUGH THE CHARGE AND FLUIDIZE IT, INLET MEANS IN THE UPPER PART OF THE CHAMBER FOR INTRODUCING MATERIAL TO BE GROUND, A DISCHARGE OUTLET IN THE UPPER ZONE OF THE CHAMBER FOR WITHDRAWING AIR AND GROUND PARTICLES OF THE MATERIAL, AND DUCT MEANS SEPARATE FROM SAID INLET MEANS FOR ADMITTING A STREAM OF AIR TO THE UPPER PART OF THE CHAMBER TO STRIKE THE TOP SURFACE OF THE CHARGE OF MATERIAL TO BE GROUND IN THE CHAMBER. 